Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Electron Distribution in BaTi0.98Zr0.02O3 Piezoceramic Using X-ray Structure Factors 1 J. Mangaiyarkkarasi1, S.Sasikumar2, R. Saravanan2 1 – PG and Research Department of Physics, NMSSVN College, Nagamalai, Madurai, India 2 – Research centre and PG Department of Physics, The Madura College, Madurai, India DOI 10.2412/mmse.81.72.958 provided by Seo4U.link
Keywords: barium titanate, X-ray diffraction, structure factor, maximum entropy method, charge density.
ABSTRACT. Single phased BaTi0.98Zr0.02O3 piezo ceramic has been synthesized by conventional high temperature solid state reaction technique at 1450 oC for 10 hrs. and characterized. Precise electronic structure and charge density distributions of BaTi0.98Zr0.02O3 have been completely analyzed through powder X-ray diffraction data (PXRD). Powder profile refinement clearly evidenced that, the prepared ceramic has been crystallized in cubic perovskite structure with space group symmetry Pm 3 m. Average grain size is calculated by Scherer formulation. The bonding nature and electron distribution around Ba and O and Ti and O are examined by adapting maximum entropy method (MEM). The predominant ionic nature of Ba-O bond and the partial covalent nature of Ti-O bond are revealed by MEM qualitatively as well as quantitatively. The optical band gap energy has been estimated as 3.11 eV from UV-vis absorption spectroscopy. Surface morphology and microstructure are also analyzed by scanning electron microscopy (SEM). Particles with irregular shapes are observed from SEM image. Atomic percentages of chemical compositions of the synthesized ceramic are further confirmed by energy dispersive X-ray spectroscopy (EDS).
Introduction. Recently, the interest towards lead-free piezoelectric ceramic materials has been increasing for electromechanical transducer devices [1]. Among them, barium zirconium titanate (BZT) ceramic has attracted great attention for its potential applications in the fabrication of microwave devices and piezoelectric transducers due to its high dielectric constant, low dielectric loss and large tunability [2]. BZT has been particularly used for multilayer ceramic capacitors (MLCCs). The addition of Zr at the lattice sites of Ti is known to be effectively changes the Curie temperature (TC) and also presents many interesting features in the dielectric and ferroelectric properties of BaTiO3 [3]. Moreover, Zr4+ ion is comparatively more stable than Ti4+ ion, hence the Ti doping at the lattice sites of Zr would depress the conduction, thereby reducing the leakage current in the BaTiO3 structure [4]. BZT ceramic materials exhibit promising infrared and optical properties which are highly essential for designing pyroelectric and electro-optical devices [5]. Microwave dielectric properties of these Zr doped BaTiO3 materials also find applications in storage capacitors for the next DRAM generation, FeRAMs and non-volatile random access memories [6]. Even though many researchers have reported the structural and dielectric related investigations, the precise electronic structure, chemical bonding and charge density distribution studies are lacking in literature. The detailed knowledge of the internal electronic structure of a material is extremely beneficial to understand the properties more clearly [7]. In this aspect, the present study focuses more on the bonding interactions between the constituent atoms of the BZT ceramic system. The accurate electronic structure of any crystalline material can be successfully elucidated by constructing the electron density from the X-ray structure factors using less biased mathematical tool such as maximum entropy method (MEM) [8].
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